The present invention concerns fastening or attachment devices for electroluminescent diodes on a sealed display table.
The optimalization of industrial processes often presumes intervention "in real time" (instantaneous) for various parameters. It is thus of prime importance to know data such as: the temperature of the pressure at one point in a process, the voltage difference or electric intensity, the opening or the closing of contacts, cut-out switches, circuit breakers, valves, the position of a switch, for example at railway points of a train; the running or stopping of the engines, alternators, ventilators or others. The display of such data is ensured especially by display tables or synoptic panels.
The reliability of such tables, in an industrial context which often presents very arduous conditions for the table material, demands that such tables be sealed. Thus display or measuring elements are protected against vapors, high temperatures and dusts.
In sealed display tables of the known type, luminous displays are often activated by glow-lamps, mounted at the rear of the tables. The glow-lamps present numerous drawbacks. Having a large surface like their supports, such does not allow their being mounted close to one another. Thus, for bulkiness reasons, they are not mounted on the optical visualization axis, which creates differences of luminosity according to the incidences under which they are observed. Furthermore, glow-lamps give off a considerable quantity of heat energy. In the devices of known type, depending on the number of glow-lamps, the cooling is carried out either by convection, with air inlet and outlet, or by forced air circulation. Further, the lifespan of the glow-lamps varies from 1500 to 5000 hours.
On the other hand, it is known to mount electroluminescent diodes on printed circuits. The printed circuit supporting the electroluminescent diodes is fastened, for example, by screws at the rear of the display table, without impairing its tightness. The positioning of the electroluminescent diodes is determined by data to be displayed. Thus this technique necessitates the creation of a new printed circuit for each display table. Furthermore, the electroluminescent diodes are no longer interchangeable to correct a diode failure or to change color following, for example, an improvement of the industrial process to be controlled. However, the lifespan of electroluminescent diodes is much longer than that of glow-lamps.
On the other hand, it is known to fasten the electroluminescent diodes by providing a hole in a display table. This embodiment presents the disadvantage of impairing the tightness of the display table. This type of embodiment is illustrated by FIG. 1.
The device according to the invention overcomes these drawbacks by allowing one to fasten an electroluminescent diode and by ensuring the electric supply at the rear of a display table. The invention is achieved by fastening the electroluminescent diode and its support in a guide which is itself fixed at the rear of the display table without impairing its tightness.